Steam stimulation of oil-bearing formations



April 30, 1968 M. F. MCCQNNELL ET AL 3,380,530

STEAM sTIMuLATIoN oF OIL-BEARING FORMATIONS 3 Sheets-Sheet 1 Filed Aprill, 1966 Wil L Hli 5 W m ,u fr f E c- 7 L l c# @wim if se /w @a a W April30, 1968 M. F. MCCQNNELL ET Al. 3,380,530

STEAM STIMULATION oF OIL-BEARING FORMATIONS 3 Sheets-Sheet 2 Filed Aprill, 1966 l W II' z 3 m 9 H 7 a 5 4 4 9/ 4 a 5 7 M a M 5 0 4 6 5 UUHIIHIIHHHU e I w M 1 rv 4 w w|.-.|. n.. la 7 7 2,/ l.. l'le 2 l 2 2 0 34 R l M w d n m u w m a w a fw.. m u m 7 n s J n. o.. n W 5 w p 78 W W fw L f f E N W. www@ ci WMM Irc/.C- 2 Mw, m 3W. if 4 a 2 Mam w QW.. mv.

April 30, 1968 M. F. MCCONNELL ET AL 3,380,530

STEAM STIMULATION OF OIL-BEARING FORMATIONS Filed April 1, 196e 3Sheets-Sheet 3 United States Patent Uffice 3,380,530 Patented Apr. 30,1968 3,380,530 STEAM STIMULATION F OIL-BEARING FORMATIONS Malcolm F.McConnell, 3940 Valley Meadow Road, Encino, Calif. 91316; Robert P.Cabeen, 4619 Grand Ave., La Canada, Calif. 91011; and Warren dstrom,Sunnyridge Road, Rolling Hills, Calif. 2

Fiied Apr. 1, 1966, Ser. No. 539,385 Claims. (Cl. 166 40) ABSTRACT 0FTHE DISCLOSURE Steam stimulation of oil bearing formations including thesteps of forcing a gas through the annulus around the steam injectionpipe at a pressure at least suflicient to prevent steam emerging fromthe lower end of the pipe from rising above a restriction in the annulusadjacent the oil strata, while restricting heat losses from the Steaminjection pipe with a column, surrounding the pipe, of `a thin metallicsheet material that is loosely confined. Steam injection pipe insulatorsincorporating such columns of thin metallic sheet that are looselyrestrained by double-walled sleeves detachably connected to the steampipe, or in an annulus permanently defined around the steam pipe, andwith provision for uid sealing ends of the insulators.

The present invention relates to the secondary recovery of hydrocarbonsfrom subsurface formations and, more specifically, to apparatus andmethods for such recovery by means of steam stimulation.

It is recognized that steam injection is an effective thermal techniqueof recovery hydrocarbons from underground formations. The heat thusadded to the formation lowers the viscosity of the oil which will thenmore readily flow into a well bore for production, which well bore maybe the same through which the steam had been injected or a bore adjacentto the steam injection well.

While the eciency of steam injection as a method of secondary recoveryis well recognized, difficulties are presented which inhibit its useeven in shallow wells and which have previously been thought to preventits use in deep wells. For example, there has heretofore always beenpresent the danger of excessive thermal expansion of the well casingleading to casing collapse and consequent loss of the well. Also,excessive temperatures of the casing tend to deteriorate `and destroythe cement bond between the casing and the formation. Another difficultymitigating against economical steam injection is the high heat lossinvolved in the transfer of the steam from the generating equipment tothe hole bottom. While techniques and apparatus for reducing such heatloss are available, the known measures are costly. Accordingly, theiruse is limited to relatively shallow wells and in most situations theuse of the insulating measures is not economically justitiable or, atbest, the prospect of profitable steam stimulation is rendered marginal.

An object of our invention is to provide an efficient method andapparatus for the recovery of hydrocarbons from sub-surface formationsby steam stimulation without danger of casing collapse or cement bondfailure, without limitation to shallow wells, and with minimum heatlosses.

Another important object of the invention is to provide a highlyefficient insulated injection tubing string which will eliminatesignificant thermal growth in oil well casings and thus avoid the dangerof casing collapse. The insulator means is further highly ellective inreducing heat losses during the transmission of the steam from the steamgenerating equipment to the hole bottom so as to effectively injectsteam at greater depths than have heretofore been possible. Accordingly,the insulatOr means of this invention permits the driving of maximumquantities of steam of the highest possible quality into thegeologicalformations of oil wells.

It is also among the objects of the invention to provide a variety ofinsulator means which is economical from the standpoint of durabilityand reusea-bility, assembly and disassembly in oil field use, -andhaving a particularly facile mode of connection to the steam injectiontubing.

A further object of the invention is to provide a method and apparatusfor steam injection of underground formations in well bores having astanding head of oil or water in the bore at the time the steaminjection string is installed and adapted to minimize heat losses insuch an environment, and to avoid any intrusion of liquid into theinsulator or damage to the insulator by said liquid head.

Yet another object of the invention is a method and apparatus permittingthe utilization of steam injection as a secondary recovery techniquewhich eliminates the need for a thermal packer.

The fore-going and other objects and advantages of the invention will beclear from the following, description when taken in connection with theannexed drawings.

FIGURE l is a schematic view showing in cross section a well boreextending into the earth and equipped with one form of the invention;

FIGURE 2 is an axial sectional view on the line 2 2 of a portion of thesteam injection tubing and associated equipment in the well of FIGURE l;

FIGURE 3 is a horizontal sectional view taken on the line 3 3 of FIGURE2 showing one means of keeping injected steam from upward passage intothe annulus between the casing and steam injection assembly;

FIGURE 4 is a schematic View of Ia well bore extending from the surfaceto an oil bearing formation and equipped with a steam injectionapparatus employed in combination with a packer;

FIGURE 5 is an axial sectional view on the line 5 5 of FIGURE 4 andillustrating a species of insulator means such as may be employed in theupper portion of the steam injection string;

FIGURE 6 is a horizontal sectional view taken on the line 6 6 of FIGURE5 and showing details of construction at one end of Ia section ofinsulator;

FIGURE 7 is a horizontal sectional view on the line 7 7 of FIGURE 5 andshowing details of construction of an insulator section at another endof an insulator section;

FIGURE 8 is an axial sectional view on the line 8 8 of FIGURE 4 showinga species of fluid-tight insulator assembly, such as may be employed inthe lower end portion of a steam injection string which is surrounded bya standing liquid.

Referring now to FIGURE 1 of the drawings, there is shown a well 10 thathas been drilled from the surface 11 of the earth into a hydrocarbonbearing formation 12. The well 10 has a casing 13 which is typicallycemented in place and which is provided at its upper end with a wellhead 14. A steam injection tubing string 15 is centrally supportedwithin the well 10, passing through the well head 14 and at its lowerend is provided with an outlet pipe 16. At the well head, the tubingstring 15 is in fiuid comrnunication with a steam supply pipe 17 which,in turn, communicates with a source (not shown) of steam from a steamgenerating unit. Thus, the steam may be driven down through the tubingstring to escape from the outlet pipe 16 for penetrating the formation12.

From the well head 14 down to the formation 12, the tubing string 15 isenclosed in a plurality of insulators 18, groups of which aregravitationally supported by a plurality of clamps 19 coaxially aihxedto the tubing string 15. An annulus 20 is thus defined between the innerwall of each insulator 18 and the surrounded section of string 15 andanother annulus 21 is defined between the insulators 18 and the casing13.

At the well head 14, the outer annulus 21 has cornmunication via a pipe22 with a source (not shown) of a gas of low thermal conductivity underpressure which may be, for example, air, nitrogen, natural gas or carbondioxide. As the annulus 20 is not perfectly sealed by the insulators 18,it will also contain gas of low thermal conductivity and the gas will besubstantially statically confined by the insulators. At the lower end ofthe tubing string 15, a restrictor in the form of an annular disc 23 iscoaxially mounted on the steam tube or to the bottom'of a clamp 19 Aandserves as a partial barrier against rising of steam emitted from thepipe 16. The compressed gas in the annulus 21 is at all times suppliedat a pressure such that the gas pressure on the upper side of theannular disc 23 exceeds the pressure of the steam on the underside ofthe disc, whereby the steam cannot rise into the annulus 21 to effectthermal expansion of the casing 13. The disc 23 should be seam welded orotherwise sealed against the tubing string 15 to keep steam out of theannulus 20, also.

Referring to FIGURE 2, each of the insulators 18 comprises an assemblyof an outer tube 26, an inner tube 25, a pair of end caps 27 and asleeve 28, which assembly contains layers of thin metallic sheet 31. Therigid parts may be made of relatively inexpensive sheet metal, forexample, 18 or 24 gauge steel, that is smoothly finished, polished orgalvanized to be of low thermal emissivity. While light in weight, theinsulators 18 are nevertheless adapted to withstand rough handling inthe field without injury to the fragile sheet 31 and will have a longservice life. Further, the construction is such that the required numberof insulators 18 can very quickly be installed and removed from thetubing string 15, these operations` being accomplished without makingany permanent connection to the tubing string.

More specifically, the insulators 18 may be made up into lengths ofapproximately l ft., for example, for use with tubing strings made up ofabout 30 ft. lengths of tubing. As can be seen from FIGURE 2, the endcaps 27 are generally U-shaped in radial cross section to provide aconfronting pair of spaced walls between which ends 0f the cylindricaltubes 25 and 26 are received. Thus, the inner tube 25 has its oppositeends telescoped around the inner walls of the end caps 27 while theouter tube 26 has its opposite ends telescopically received within theradially outer walls of the pair of end caps 27. Preferably, the ends ofthe inner tube 25 are not soldered or welded to the end caps 27, norotherwise secured, so as to allow differential thermal expansion betweentubes 25 and 26. In order to hold the end caps 27 and tubes 25 and 26 inassembled relationship, it is preferable to merely spot weld or spotsolder opposite ends of the outer tube 26 tothe end caps 27, asindicated, for example, at 30. At the upper end of the insulator 18,spot welding 30 may also be ernployed to secure a sleeve 28 to theassembly, this sleeve being of an internal diameter such that its lowerend telescopically receives the upper end cap 27, whereby the sleeve 28coaxially projects upwardly to telescopically slidably receive thereinthe lower end of another insulator assembly 18. Adjacent insulators 18are thus axially interconnected and supported one upon another.

The insulators 1S provide a substantially dead gas space in the annulusdefined between the inner tube 25 and the outer tube 26, thus inhibitingtransfer of conductive thermal energy from the inner shell to the outershell. Transfer of thermal energy by radiation is inhibited by wrappingthe inner tube 25 in a layer or layers of a very thin sheet material 31of a metallic substance which is preferably highly polished on at leastone side. For example, ordinary aluminum foil of a few mils thickness,e.g. 2-3 mils, such as employed for kitchen use, may be used with verysatisfactory results. In assembling an insulator 18, a length of thesheet material 31 of the same length as the inner tube 25 is wrappedaround the inner shell. The inner tube 25 is loosely wrapped in thesheet 31 to achieve several spaced layers of the sheet 31 as indicatedin FIGURE 2, or at least to achieve discontinuous surface contactbetween adjacent layers of the sheet 31. The desired effect will beenhanced by inducing wrinkling in the metallic sheet 31 during thewrapping operation, thus minimizing Contact points and maximizing theinclusion of static gas spaces between adjacent layers of the sheet.Thereafter, when the wrapped inner tube 25 is surrounded by the outertube 26, the sheet 31 is confined and restrained into elongated tubularconfiguration against significant buckling when the insulator 18 isplaced in a vertical position.

Each of the support clamps 19 preferably comprises a pair ofsplit-collar castings 32, whose plan configuration is shown in FIGURE 3.Each split-collar 32 is of a substantially uniform web thicknessproviding an almost semicylindrical inner wall 33 of a radius to bematingly engageable with one side of the tubing string 15. At axiallyopposite ends of the wall 33, the web ofthe casting merges into almostsemi-circular flat portions 34 and 35, disposed in diametral planes. Thecasting is also integrally formed with three angularly spaced apartaxially and radially extending web portions 36, 37 and 38 extendingoutwardly from the inner wall 33 and between the flat portions 34 and35. These webs 36, 37 and 38 extend radially outwardly beyond the fiatportions 34 and 35 to merge into axially elongated portions defining adiameter around the fiat portions 34 and 35, such as to telescopicallyreceive the upper and lower ends of adjacent insulators 18. The webs 36and 37 also form four buffers which serve to keep the tubing andinsulator assembly approximately centralized within the casing.

When a pair of the castings 32 are placed on opposite sides of thetubing of the string 15 they can be clamped together and onto the tubingby a suitable fastener means 39, such as pairs of nuts and bolts passingthrough suitably located holes formed in the webs 36 and 38, thusdefining the support clamp assembly 19. As will be apparent, as thetubing string 15 is made up at the well head a support clamp 19 rnay beconnected thereto irnmediately above the outlet pipe 16 and the annularrestrictor disc 23. Thereafter, the tubing string 15 as it is made uphas successive sections of the insulators 18 sleeved thereover andsleeved together until an appropriate number of the insulators 18 aregravitationally supported by the clamp 19For example, we have found thateach clamp 19 can very readily support approximately ft. of slip-oninsulator sections 18 after which a new clamp 19 is afixed to theinjection string 15 to support another 100 ft. or so of insulators 18.The assembly of the tubing string 15 and insulators 18 is thus continueduntil the correct string length for disposing the outlet pipe 16opposite the formation 12 is achieved.

After the insulated tubing string 15 is made up, the steam line 17 isconnected to a source of steam at a suitable pressure for penetratingthe formation 12 and the gas pipe 22 is connected to a source of asuitable gas under pressure for injection into the annulus 21. Thepressures of injected steam and gas on opposite sides of the restrictordisc 23 are such that the steam is prevented from escaping upwardlyaround the annular disc 23. Further, the higher pressure of the injectedgas passing through the annulus augments the steam pressure thusencouraging the penetration of high quality steam into the formation 12.

FIGURE 4 illustrates another embodiment of the steam injection system ofour invention. In this case, a well bore extends from a ground surface11 down to a formation 12. The well is provided with the usual casing 13which is capped by a well head 14 through which a tubing string 15'passes. The upper end of the string is connected to a pipe 17communicating with a source of steam. At the lower end of the string 15'just above the formation 12 desired to be stimulated, a packer is set inthe casing 13 and through which the injection string 15 passes tocommunicate with the outlet pipe 16.

The system of FIGURE 4 differs from the system of FIGURE 1 in that thelower end of the annulus 21 above the formation 12 is sealed oft" by thepacker 40 and the annulus 21 is not communicated to a source of gasunder pressure. Rather, the annulus 21 may be vented to the atmosphereat the well head 14 or the annulus may be evacuated if desired. Foreconomy of illustration, the tubing string 15 is insulated in FIIG- URE4 by two types of insulator 41 and 42, the former being shown in FIGURE5 and the latter in FIGURE 8. However, it is to be understood that thesystems of FIG- URE 1 or 4 may be employed with the insulator 10,insulator 41 or insulator 42, or any combination thereof. Forconvenience of description, it will be assumed that the system of FIGURE4 is provided with the insulators 41 in upper portions of the string andthat the lower end of the well bore is provided with a standing head ofa fluid, in which environment the use of the insulators 42 of FIGURE 8is preferable.

The insulator 41 of FIGURE 5 is of a type which is mounted integrallywith the individual sections of pipe making up the tubing string 15 butwhich may be so mounted without the necessity for any permanentconnection of the insulating means to the pipe and particularly withoutnecessity for any welding such as could be locally injurious to thesections of pipe. In many situations welding of the insulator to thetubing is permissible and may be preferable from the economicstandpoint. Functioning of the insulation system is not adverselyaffected. While the insulating means 41 may more conveniently beintegrated with the sections of pipe in a shop, the construction is suchthat the insulator may be mounted to the sections of pipe at the wellsite.

In FIGURE 5, there are shown two sections of conventional pipe, 44 and45, fastened together by a coupling 46. The insulator 41 includes anelongated cylindrical outer shell 47 which at its lower end, externallymounts an axially slidable sleeve 48. This assembly is hung at its upperend adjacent the upper end of a section, such as the pipe 44 of thestring 15 in the following manner. A strip 49 of an insulating material,for example, asbestos tape, is wound circumferentially around thesection of pipe 44 approximately 2 ft. beneath the area of a coupling46. Thereafter, a split collar 50, that is L-shaped in radial section,is placed around the strip 49 with the cylindrical portion of the collar50 embracing the tape. At the confronting ends of the split collar 50, apair of radially and axially disposed ears 51 are affixed thereto, as bywelding, and are formed with a pair of aligned holes for the receptionof a suitable fastener means 52 which, upon tightening, securely butdetachably clamps the collar 50 in place.

In the lower end portion of the section of pipe, approximately 2 ft.above and adjacent the coupling 46, another piece of insulating tape 53is wrapped around the circumference. The axial spacing of the wrap oftape 53 beneath the wrap of tape 49 is approximately equal to the lengthof the cylindrical shell 47 to be sleeved over the piece of pipe 44.Thereafter, the piece of pipe 44 is wrapped in a length of thin metallicsheet material 54 throughout the area between the pairs of tapes 49 and53, in the same manner as previously described in connection with theinsulator 10. Thereafter, the shell 47 is sleeved over the looselywrapped and wrinkled layers of sheet material 54 until the upper endabuts the underside of the radially disposed portion of the collar 50.The shell 47 is then tack-welded at its upper end to angularly spacedapart portions of the underside of the split collar 50, so that when thesection of pipe 44 is in the vertical posiion, the shell 47 hangs fromthe collar.

At the lower end of the shell 47, a ring 55, which may be made up ofarcuate segments, is affixed as by tackwelding 56 within the shell toclose its lower end. The internal diameter of the ring is such as toprovide a close or sliding clearance at 57 on the surface of the pieceof tape 53. The axial dimension of the tape 53 should Ibe at least greatenough to cover the full range of the difference in thermal elongationbetween the piece ot steam injection pipe 44 and the shell 47 so thatdespite the greater elongation of the steam injection pipe, because ofits higher temperature, the piece of tape 53 will at all times bedisposed as an insulating barrier between the steam injection pipe andthe ring 55.

As is shown in FIGURE 5, after sections of the string 15 have beencoupled together the area between the insulators 41 and including thecoupling 46 may be insulated -by pulling the slidable sleeve 48 into theposition shown so that a tapered or crimped lower end S8 of the sleevegravitationally rests on the radially disposed portion of the collar5t)` therebelow. In order to provide clearance for such abutment, thecrimped portion 58 is notched, as indicated at S9, to receive the ears51 of the collar therein. While not essential for most applications, ifdesired, a layer or layers of metallic sheet material 54 may be looselywrapped around the coupled ends of the pipes but care should be taken soas to avoid creating convenient conduction paths through tightly packedlayers for the transfer of heat from the coupling to the sleeve 48. Thesleeve 4S should be freely slidable on the shell 47 when heated so thatits weight will, at all times, cause it to bear on top of the collar 50.If desired, a plurality of outriggers 60 may be tack-welded in equallycircuiarly spaced apart relationship to the upper end of the shell 47 tomaintain the string and insulator 41 in central coaxial relationship tothe casing 13.

The insulator 41 of FIGURE 5, like the insulator 10 of FIGURE 2, mayhave its rigid parts made of relatively light gauge sheet metal,preferably galvanized steel, and accordingly, is extremely light inweight and relatively inexpensive while at the same time constituting ahighly efficient insulator which eliminates any significant thermalstress in the casing 13 during steam injection. In this connection, ascompared to the double wall insulator 10, it will -be observed that thesingle wall insulator 41 provides an arrangement to dispose a greatnumber of layers of metallic foil or sheet in loosely wound columnarformation of smaller diameter. While the insulator 41 is not sealedagainst the penetration of liquids which may be standing in the bottomof the well bore, its construction and advantages may be realized in auid tight construction by the modication shown in FIGURE 8.

The insulator 42 is of a construction permanently integrated with thetubing string 15. As shown in FIGURE 8, the tubing string 15 includesconventional pipe sections and 66 coupled together at 67 and eachincorporating an insulator means 42. Each pipe section, at its upper endapproximately 2 ft. beneath the coupling 67 has a ring 63 coaxiallyexternally affixed thereto as by continuous welding 68. At its lower endapproximately 2 ft. above the coupling area, each pipe section iswrapped with a length of insulating tape 53' spaced from the ring 63 adistance approximately the same as the length of an outer cylindricalshell 69. The shell 69 preferably comprises a length of seamless pipe,whose internal diameter is such as to enable the upper end of the tubeto be telescopically slidable over the periphery of the ring 63 andpermanently aiiixed thereto by a continuous seam-weld 79, suchconnection taking place after the pipe section has been loosely wrappedin a layer or layers of metallic foil or sheet 71 in the length of thetube between the ring 63 and the tape 53. At its lower end, thecylindrical shell internally mounts a ring 55', which may also be of asegmented construction, the ring being welded in place and like the ringS having a close lit on or sliding engagement with the insulating tapeS3' which the ring surrounds.

Each shell 69 at its lower end externally mounts an axially slidablesleeve 7 3, which in view of the differential pressures to which thedevice may be subjected is also preferably made of a length of pipegreater in length than the space between adjacent ends of pipes 65 and66, so as to span this area and the coupling 67. The sleeve 73, adjacentits lower end, is internally provided with a metal bumper ring securedin place by brazing, for exr ample, and spaced from the lower edge ofthe sleeve a sutiicient distance so that when the sleeve is lowered totelescopically receive the upper end of a lower adjacent shell therein,a generous overlap is provided sutiicient to give a range of movementgreat enough to accommodate relative movement of the parts upon thermalex pansion.

At its opposite ends, the sleeve 73 is encased in a pair of axiallyelongated tubular seals of an elastomeric material as, for example,neoprene, of a relaxed diameter smaller than the diameter of thecylindrical shells 69. As the joint at 67 is made up, it will beappreciated that the sleeve 73 is raised from the position shown inFIGURE 8 with its bumper 74 abutting the lower end of its associatedshell 69. At this point, the pair of seals 75 are in a position rolledback upon the sleeve 73. Then, after the joint has been made up tointerconnect the pipes 65 and 66 and after, if desired, an additionallayer or layers of metallic foil or sheet 71 have been loosely wrappedaround the exposed area, between insulators 42, the sleeve 73 can belowered to the position shown in FIGURE 8. In this connection, becauseof the small clearance between the bumper '74 and the enlargement at thecoupling 67, it is preferable that no layers 71 be placed around thecoupling 67. After the sleeve 73 is in position with its bumper 74abutting the upper end of the adjoining shell 69, the pair of seals 75have their roller back portions rolled onto the adjacent surface of acylindrical shell, thereby sealing the joint. Thereafter, each of theseals 75 has a hoseclamp 76 wrapped around each of its ends to insurethe integrity of the seal.

Referring to FIGURE 4, if it be assumed that a standing head of liquidis in the lower portion of the well bore, the steam injection tubingstring can be made up with an appropriate number of the sealedinsulators 42 for the lower portion of the string exposed to thestanding head of liquid while the upper portion of the string may bemade up using the insulators 41. The packer 40 being set whereby to sealoff the producing length of the well bore from the annulus 21'thereabove, steam may now be introduced thro-ugh the steam pipe 17 forinjection into the oil bearing strata 12'. For example, assuming a steamtemperature of 450 F. the cylindrical shell 69 and sleeve 73 of theinsulator `42 will not rise more than about 650 F. above the normalambient temperature of the surrounding liquid in the well bore. Further,if no liquid is present in the well bore, the temperature of the casing13' may be held within about of the ambient geothermic temperature.

The systems and apparat-us illustrated and described herein are to betaken only as typical examples of the practice of our invention and arenot to be taken in a limiting sense. While we have set forth whatweconsidered to be the best modes of our invention, various modificationsOf the systems and apparatus described will undoubtedly occur to thoseskilled in the art to whom equivalents will occur. Accordingly, we donot wish to be limited except in accordance with the spirit and scope ofthe following claims.

5 We claim:

1. A process of raising the temperature of hydrocarbons in a sub-surfaceformation by steam injection through a well bore from the surface to theformation, including:

defining steam conduit means, in a casing of the well bore, from thesurface to the formation and spaced from the casing;

forcing steam downwardly through the conduit means to be releasedadjacent the formation;

forcing a gas downwardly through the space between the casing and theconduit means;

restricting the tiow of the gas at a position within the casing justabove the formation;

maintaining a pressure of the gas sufficient to prevent steam emergingfrom the conduit means from rising above the position of restriction ofthe gas fiow;

and -rnaintaing a steam lpressure sufficient to force steam emergingfrom the conduit means into the formation.

2. A process as in claim 1 in which the pressure of the gas is highenough to force the gas downwardly past the position of restriction andinto the formation.

3. The process of claim 1 which includes:

defining the conduit means by coupling together several lengths of pipe;

surrounding the pipes of the conduit means between the surface and theposition of gas flow restriction with a column for each pipe of ametallic sheet material having a smooth finish on at least one side andof a material thinness incapable of vertically supporting the columnlength, each column having a minimum length, approximately, co-extensivewith the uncoupled area of the pipe;

and supporting the columns of thin metallic sheet material againstbucking and against displacement out of a position in which the columnsare in spaced relation to the casing.

4. A thermally improved process of raising the temperature ofhydrocarbons in a sub-surface formation by steam injection through awell bore from the surface to the formation, including:

defining steam conduit means in a casing of the well bore, from thesurface to the formation and spaced from the casing by coupling togethersections of conduits;

reducing heat losses from the steam conduit means by surrounding each ofthe sections of conduits, throughout approximately at least the lengthof the sections other than their coupled areas, in that portion of theconduit means from the surface down to a location immediately above theformation, with a column of a metallic sheet material having a smoothfinish of low thermal emissivity on at least one side and of a materialthinness incapable of substantially erect-ly supporting the column;

loosely confining the column of thin metallic sheet material of each ofthe sections against collapsing under its own weight and againstdisplacement out of a position in which the column is in spaced relationto the casing;

forcing steam downwardly through the conduit means to be releasedadjacent the formation;

preventing rising of steam emerging from the conduit means beyond thelocation immediately above the formation to force the steam into theformation.

5. The process of claim 4 which includes surrounding each of thesections of conduit with a plurality of layers of the thin metallicsheet column material successively loosely enclosing one another, theadjacent layers being arranged to have areas of separation to providecapacity for reception of a gas of low thermal conductivity betweensuccessive layers of the sheet material.

6. A process as in claim 5 which includes:

defining an annular space between the column and the section of conduitand substantially completely enclosing the volume around each section ofconduit that is occupied by the column and the annular space with asheet material that is impervious to the passa-ge of uids tosubstantially statically confine a gas of low thermal conductivity.

7. The process of claim 5 which includes substantially completelysealing the space around each section of conduit that is occupied by thegroup of layers of thin sheet metal column material to confine thecolumn and contain a gas of low thermal conductivity.

8. A process as in claim 4 that includes:

limiting the length of the column of thin metallic sheet material to thecircumferential area of the section of conduit exclusive of the coupledareas of adjacent sections of conduit and enclosing an annular volumebetween adjacent ends of a pair of the columns and around the coupledareas of the corresponding sections of conduit with a rigid sheet.material that is impervious to the passage of fluids to contain asubstantially static volume of a gas of low thermal conductivity.

9. A process as in claim 8 that includes:

sealing the rigid sheet material and the static volume of -gas enclosedtherein against penetration thereinto by a liquid.

10. An insulator for inhibiting heat losses in an oil well steaminjection pipe comprising:

a sheet arranged in elongated tubular form and made of metallic materialhaving opposite surfaces adapted for a low rate of thermal emissivityand of a thinness incapable of substantially withstanding buckling ofthe tubularly ar-ranged sheet when vertically disposed;

and an elongated rigid .means of substantially tubular configurationarranged coaxially with said tubularly arranged sheet and adapted toloosely restrain the sheet into tubular form in order to minimize areasof Contact between said sheet and said rigid means.

11. An insulator as in claim 10 that includes:

a section of steam injection pipe extending coaxially inside of thetubularly arranged sheet, the wall of said pipe comprising a portion ofsaid rigid means restraining the sheet in tubular form.

12. An insulator as in claim 10 in which:

the rigid means restraining the sheet includes an elongated tube of arigid material having smooth surfaces to -be adapted for a low rate ofthermal emissivity, the tube coaxially surrounding the tubularlyarranged sheet,

and a connecting means supporting one end of the tube and adapted forcoaxially connecting to a steam pipe therethrough to support the tube incoaxial relationship to the steam pipe.

13. An insulator as in claim 12 in which:

the elongated tube at one end coaxially supports a tubular sleeveextending beyond the one end of the tube for contact with an adjacentend of a second tube.

14. An insulator as in claim 13 in which:

the sleeve is telescopically slidably connected to one end of the tubeto allow relative movement therebetween in response to differentialthermal elongation of the sleeve and tube and to be adapted for coaxialextendability from the tube to be engageable with an adjacent end of asecond tube.

15. An insulator as in claim 14 in which:

a sealing means is provided on one end of the sleeve forcircumferentially sealing the one end of the sleeve and the tube againstpenetration by fluids when the sleeve is in coaxially extended position.

16. An insulator as in claim 12 that includes:

a section of steam injection pipe extending coaxially inside of thetubularly arranged sheet, the wall of said pipe comprising a portion ofsaid rigid means restraining the sheet in tubular form,

the section of steam pipe having a circumferential area of predeterminedaxial length carrying an insulating layer of a material of low thermalconductivity,

the other end of the tube internally coaxially mounting a diametricallydisposed ring whose radially inner edge closely confronts the insulatinglayer of the steam pipe,

the axial dimension of the insulating layer being suicient to maintain aportion of the insulating layer disposed between the ring and the steampipe when the tube and steam pipe are differently thermally elongated.

17. An insulator as in claim 12 in which:

the connecting means supporting the tube comprises a clamping deviceadapted for fastening to a steam pipe and to extend circumferentiallyand radially outwardly from the steam pipe,

the clamping device and the lower end of the tube having matinglyengageable portions adapted to gravitationally support the tube on theclamping device and in coaxial spaced relationship to a steam pipe,

and one end of the tube mounts a sleeve adapted and arranged fortelescopically coaxially interconnecting the adjacent end of a pair oftubes whereby a plurality of the tubes can be gravitationally supportedon one of the clamping devices.

18. An insulator as in claim 12 in which:

the connecting means c-omprises an annular ring internally secured tothe upper end of the tube and connected to a steam pipe that extendscoaxially inside the tube and comprises a portion of the rigid meansrestraining the sheet in tubular form,

the tube depending gravitationally from the ring in coaxially annularlyspaced relationship to the steam pipe.

19. An insulator as in claim 10 in which:

the rigid means restraining the sheet in tubular form comprises acylinder of an internal diameter adapted to dene an annular gas spacewith a steam pipe to be coaxially extended therethrough.

20. An insulator as in claim 10 in which:

the rigid means comprises a coaxially telescoped pair of metal cylindersdening `an annular gas space in which space the metallic sheet ofelongated tubular form is loosely and substantially coaxially conned;

and a ca-p is mounted at each of the opposite ends of the pair ofcylinders to substantially close the opposite ends of the annular gasspace.

21. In an oil well steam injection apparatus, the combinationcomprising:

'a steam injection tubing string comprising coupled sections of pipe;

a plurality of rigid elongated cylindrical heat shields made of a sheetmaterial of low thermal conductivity that have been smoothly finis-hedto be adapted for low thermal emissivity;

and a plurality of connecting means vertically spaced along the tubingstring and each connected between one of the pipes and one of theshields to support a shield in annularly spaced relationship to thepipe.

22. An apparatus as in claim 21 in which each of the connecting meansgravitationally supports a plurality of the heat shields.

23. An apparatus as in claim 21 in which:

, there is one of the connecting means between each t0 plpe and eachshield and each shield is shorter than and disposed between oppositeends of the associated pipe. 24. An apparatus as in claim 21 having aplurality of 75 sleeves each of which is mounted coaxially on an end of1 1 1 2 one of the shields in annularly spaced relationship to theReferences Cited string and is adapted for engagement with the adjacentend UNITED STATES PATENTS of another shield.

2S. An apparatus as in claim 21 in which each of the 21041778 7/1936Hayden 1353*-149 X shields encloses a tubularly arranged sheet ofmetallic 5 2,148,717 2/1939 Whitney 165-11 material having smoothsurfaces and of a material thinness 2,790,464 4/1957 Stephens et al13S-149 X incapable of substantially withstanding buckling of the2,930,407 3/1960 Conley et al. 13S-149 X tubularly arranged sheet whenvertically disposed, 3,142,336 7/1964 Doscher 166-11 the sheet beingloosely confined in tubular form in the 3,289,849 10/ 1966 Rendos et al13S-149 annulus between the shield and the pipe to surround l() the pipeand divide the annulus into gas spaces. STEPHEN I- NOVOSAD, Primal?Examiner

